Wash Boring ~ this is a method of removing loosened soil from a
bore hole using a strong jet of water or bentonite which is a
controlled mixture of fullers earth and water. The jetting tube is
worked up and down inside the bore hole, the jetting liquid
disintegrates the subsoil which is carried in suspension up the
annular space to a settling tank. The settled subsoil particles can
be dried for testing and classification. This method has the
advantage of producing subsoil samples which have not been
disturbed by the impact of sampling shells however it is not suitable
for large gravel subsoils or subsoils which contain boulders.
Mud-rotary Drilling ~ this is a method which can be used for rock
investigations where bentonite is pumped in a continuous flow
down hollow drilling rods to a rotating bit. The cutting bit is kept
in contact with the bore face and the debris is carried up the
annular space by the circulating fluid. Core samples can be
obtained using coring tools.
Core Drilling ~ water or compressed air is jetted down the bore
hole through a hollow tube and returns via the annular space.
Coring tools extract continuous cores of rock samples which are
sent in wooden boxes for laboratory testing.
Soil Investigation